<?php

/**
 * @file
 * Database interface code for SQLite embedded database engine.
 */

/**
 * @ingroup database
 * @{
 */

include_once DRUPAL_ROOT . '/includes/database/prefetch.inc';

/**
 * Specific SQLite implementation of DatabaseConnection.
 */
class DatabaseConnection_sqlite extends DatabaseConnection {

	/**
	 * Whether this database connection supports savepoints.
	 *
	 * Version of sqlite lower then 3.6.8 can't use savepoints.
	 * See http://www.sqlite.org/releaselog/3_6_8.html
	 *
	 * @var boolean
	 */
	protected $savepointSupport = FALSE;

	/**
	 * Whether or not the active transaction (if any) will be rolled back.
	 *
	 * @var boolean
	 */
	protected $willRollback;

	/**
	 * All databases attached to the current database. This is used to allow
	 * prefixes to be safely handled without locking the table
	 *
	 * @var array
	 */
	protected $attachedDatabases = array();

	/**
	 * Whether or not a table has been dropped this request: the destructor will
	 * only try to get rid of unnecessary databases if there is potential of them
	 * being empty.
	 *
	 * This variable is set to public because DatabaseSchema_sqlite needs to
	 * access it. However, it should not be manually set.
	 *
	 * @var boolean
	 */
	var $tableDropped = FALSE;

	public function __construct(array $connection_options = array()) {
		// We don't need a specific PDOStatement class here, we simulate it below.
		$this->statementClass = NULL;

		// This driver defaults to transaction support, except if explicitly passed FALSE.
		$this->transactionSupport = $this->transactionalDDLSupport = !isset($connection_options['transactions']) || $connection_options['transactions'] !== FALSE;

		$this->connectionOptions = $connection_options;

		// Allow PDO options to be overridden.
		$connection_options += array(
				'pdo' => array(),
		);
		$connection_options['pdo'] += array(
				// Force column names to lower case.
				PDO::ATTR_CASE => PDO::CASE_LOWER,
				// Convert numeric values to strings when fetching.
				PDO::ATTR_STRINGIFY_FETCHES => TRUE,
		);
		parent::__construct('sqlite:' . $connection_options['database'], '', '', $connection_options['pdo']);

		// Attach one database for each registered prefix.
		$prefixes = $this->prefixes;
		foreach ($prefixes as $table => &$prefix) {
			// Empty prefix means query the main database -- no need to attach anything.
			if (!empty($prefix)) {
				// Only attach the database once.
				if (!isset($this->attachedDatabases[$prefix])) {
					$this->attachedDatabases[$prefix] = $prefix;
					$this->query('ATTACH DATABASE :database AS :prefix', array(':database' => $connection_options['database'] . '-' . $prefix, ':prefix' => $prefix));
				}

				// Add a ., so queries become prefix.table, which is proper syntax for
				// querying an attached database.
				$prefix .= '.';
			}
		}
		// Regenerate the prefixes replacement table.
		$this->setPrefix($prefixes);

		// Detect support for SAVEPOINT.
		$version = $this->query('SELECT sqlite_version()')->fetchField();
		$this->savepointSupport = (version_compare($version, '3.6.8') >= 0);

		// Create functions needed by SQLite.
		$this->sqliteCreateFunction('if', array($this, 'sqlFunctionIf'));
		$this->sqliteCreateFunction('greatest', array($this, 'sqlFunctionGreatest'));
		$this->sqliteCreateFunction('pow', 'pow', 2);
		$this->sqliteCreateFunction('length', 'strlen', 1);
		$this->sqliteCreateFunction('md5', 'md5', 1);
		$this->sqliteCreateFunction('concat', array($this, 'sqlFunctionConcat'));
		$this->sqliteCreateFunction('substring', array($this, 'sqlFunctionSubstring'), 3);
		$this->sqliteCreateFunction('substring_index', array($this, 'sqlFunctionSubstringIndex'), 3);
		$this->sqliteCreateFunction('rand', array($this, 'sqlFunctionRand'));

		// Execute sqlite init_commands.
		if (isset($connection_options['init_commands'])) {
			$this->exec(implode('; ', $connection_options['init_commands']));
		}
	}

	/**
	 * Destructor for the SQLite connection.
	 *
	 * We prune empty databases on destruct, but only if tables have been
	 * dropped. This is especially needed when running the test suite, which
	 * creates and destroy databases several times in a row.
	 */
	public function __destruct() {
		if ($this->tableDropped && !empty($this->attachedDatabases)) {
			foreach ($this->attachedDatabases as $prefix) {
				// Check if the database is now empty, ignore the internal SQLite tables.
				try {
					$count = $this->query('SELECT COUNT(*) FROM ' . $prefix . '.sqlite_master WHERE type = :type AND name NOT LIKE :pattern', array(':type' => 'table', ':pattern' => 'sqlite_%'))->fetchField();

					// We can prune the database file if it doesn't have any tables.
					if ($count == 0) {
						// Detach the database.
						$this->query('DETACH DATABASE :schema', array(':schema' => $prefix));
						// Destroy the database file.
						unlink($this->connectionOptions['database'] . '-' . $prefix);
					}
				}
				catch (Exception $e) {
					// Ignore the exception and continue. There is nothing we can do here
					// to report the error or fail safe.
				}
			}
		}
	}

	/**
	 * SQLite compatibility implementation for the IF() SQL function.
	 */
	public function sqlFunctionIf($condition, $expr1, $expr2 = NULL) {
		return $condition ? $expr1 : $expr2;
	}

	/**
	 * SQLite compatibility implementation for the GREATEST() SQL function.
	 */
	public function sqlFunctionGreatest() {
		$args = func_get_args();
		foreach ($args as $k => $v) {
			if (!isset($v)) {
				unset($args);
			}
		}
		if (count($args)) {
			return max($args);
		}
		else {
			return NULL;
		}
	}

	/**
	 * SQLite compatibility implementation for the CONCAT() SQL function.
	 */
	public function sqlFunctionConcat() {
		$args = func_get_args();
		return implode('', $args);
	}

	/**
	 * SQLite compatibility implementation for the SUBSTRING() SQL function.
	 */
	public function sqlFunctionSubstring($string, $from, $length) {
		return substr($string, $from - 1, $length);
	}

	/**
	 * SQLite compatibility implementation for the SUBSTRING_INDEX() SQL function.
	 */
	public function sqlFunctionSubstringIndex($string, $delimiter, $count) {
		// If string is empty, simply return an empty string.
		if (empty($string)) {
			return '';
		}
		$end = 0;
		for ($i = 0; $i < $count; $i++) {
			$end = strpos($string, $delimiter, $end + 1);
			if ($end === FALSE) {
				$end = strlen($string);
			}
		}
		return substr($string, 0, $end);
	}

	/**
	 * SQLite compatibility implementation for the RAND() SQL function.
	 */
	public function sqlFunctionRand($seed = NULL) {
		if (isset($seed)) {
			mt_srand($seed);
		}
		return mt_rand() / mt_getrandmax();
	}

	/**
	 * SQLite-specific implementation of DatabaseConnection::prepare().
	 *
	 * We don't use prepared statements at all at this stage. We just create
	 * a DatabaseStatement_sqlite object, that will create a PDOStatement
	 * using the semi-private PDOPrepare() method below.
	 */
	public function prepare($query, $options = array()) {
		return new DatabaseStatement_sqlite($this, $query, $options);
	}

	/**
	 * NEVER CALL THIS FUNCTION: YOU MIGHT DEADLOCK YOUR PHP PROCESS.
	 *
	 * This is a wrapper around the parent PDO::prepare method. However, as
	 * the PDO SQLite driver only closes SELECT statements when the PDOStatement
	 * destructor is called and SQLite does not allow data change (INSERT,
	 * UPDATE etc) on a table which has open SELECT statements, you should never
	 * call this function and keep a PDOStatement object alive as that can lead
	 * to a deadlock. This really, really should be private, but as
	 * DatabaseStatement_sqlite needs to call it, we have no other choice but to
	 * expose this function to the world.
	 */
	public function PDOPrepare($query, array $options = array()) {
		return parent::prepare($query, $options);
	}

	public function queryRange($query, $from, $count, array $args = array(), array $options = array()) {
		return $this->query($query . ' LIMIT ' . (int) $from . ', ' . (int) $count, $args, $options);
	}

	public function queryTemporary($query, array $args = array(), array $options = array()) {
		// Generate a new temporary table name and protect it from prefixing.
		// SQLite requires that temporary tables to be non-qualified.
		$tablename = $this->generateTemporaryTableName();
		$prefixes = $this->prefixes;
		$prefixes[$tablename] = '';
		$this->setPrefix($prefixes);

		$this->query(preg_replace('/^SELECT/i', 'CREATE TEMPORARY TABLE ' . $tablename . ' AS SELECT', $query), $args, $options);
		return $tablename;
	}

	public function driver() {
		return 'sqlite';
	}

	public function databaseType() {
		return 'sqlite';
	}

	public function mapConditionOperator($operator) {
		// We don't want to override any of the defaults.
		static $specials = array(
				'LIKE' => array('postfix' => " ESCAPE '\\'"),
				'NOT LIKE' => array('postfix' => " ESCAPE '\\'"),
		);
		return isset($specials[$operator]) ? $specials[$operator] : NULL;
	}

	public function prepareQuery($query) {
		return $this->prepare($this->prefixTables($query));
	}

	public function nextId($existing_id = 0) {
		$transaction = $this->startTransaction();
		// We can safely use literal queries here instead of the slower query
		// builder because if a given database breaks here then it can simply
		// override nextId. However, this is unlikely as we deal with short strings
		// and integers and no known databases require special handling for those
		// simple cases. If another transaction wants to write the same row, it will
		// wait until this transaction commits.
		$stmt = $this->query('UPDATE {sequences} SET value = GREATEST(value, :existing_id) + 1', array(
				':existing_id' => $existing_id,
		));
		if (!$stmt->rowCount()) {
			$this->query('INSERT INTO {sequences} (value) VALUES (:existing_id + 1)', array(
					':existing_id' => $existing_id,
			));
		}
		// The transaction gets committed when the transaction object gets destroyed
		// because it gets out of scope.
		return $this->query('SELECT value FROM {sequences}')->fetchField();
	}

	public function rollback($savepoint_name = 'drupal_transaction') {
		if ($this->savepointSupport) {
			return parent::rollBack($savepoint_name);
		}

		if (!$this->inTransaction()) {
			throw new DatabaseTransactionNoActiveException();
		}
		// A previous rollback to an earlier savepoint may mean that the savepoint
		// in question has already been rolled back.
		if (!in_array($savepoint_name, $this->transactionLayers)) {
			return;
		}

		// We need to find the point we're rolling back to, all other savepoints
		// before are no longer needed.
		while ($savepoint = array_pop($this->transactionLayers)) {
			if ($savepoint == $savepoint_name) {
				// Mark whole stack of transactions as needed roll back.
				$this->willRollback = TRUE;
				// If it is the last the transaction in the stack, then it is not a
				// savepoint, it is the transaction itself so we will need to roll back
				// the transaction rather than a savepoint.
				if (empty($this->transactionLayers)) {
					break;
				}
				return;
			}
		}
		if ($this->supportsTransactions()) {
			PDO::rollBack();
		}
	}

	public function pushTransaction($name) {
		if ($this->savepointSupport) {
			return parent::pushTransaction($name);
		}
		if (!$this->supportsTransactions()) {
			return;
		}
		if (isset($this->transactionLayers[$name])) {
			throw new DatabaseTransactionNameNonUniqueException($name . " is already in use.");
		}
		if (!$this->inTransaction()) {
			PDO::beginTransaction();
		}
		$this->transactionLayers[$name] = $name;
	}

	public function popTransaction($name) {
		if ($this->savepointSupport) {
			return parent::popTransaction($name);
		}
		if (!$this->supportsTransactions()) {
			return;
		}
		if (!$this->inTransaction()) {
			throw new DatabaseTransactionNoActiveException();
		}

		// Commit everything since SAVEPOINT $name.
		while($savepoint = array_pop($this->transactionLayers)) {
			if ($savepoint != $name) continue;

			// If there are no more layers left then we should commit or rollback.
			if (empty($this->transactionLayers)) {
				// If there was any rollback() we should roll back whole transaction.
				if ($this->willRollback) {
					$this->willRollback = FALSE;
					PDO::rollBack();
				}
				elseif (!PDO::commit()) {
					throw new DatabaseTransactionCommitFailedException();
				}
			}
			else {
				break;
			}
		}
	}

}

/**
 * Specific SQLite implementation of DatabaseConnection.
 *
 * See DatabaseConnection_sqlite::PDOPrepare() for reasons why we must prefetch
 * the data instead of using PDOStatement.
 *
 * @see DatabaseConnection_sqlite::PDOPrepare()
 */
class DatabaseStatement_sqlite extends DatabaseStatementPrefetch implements Iterator, DatabaseStatementInterface {

	/**
	 * SQLite specific implementation of getStatement().
	 *
	 * The PDO SQLite layer doesn't replace numeric placeholders in queries
	 * correctly, and this makes numeric expressions (such as COUNT(*) >= :count)
	 * fail. We replace numeric placeholders in the query ourselves to work
	 * around this bug.
	 *
	 * See http://bugs.php.net/bug.php?id=45259 for more details.
	 */
	protected function getStatement($query, &$args = array()) {
		if (count($args)) {
			// Check if $args is a simple numeric array.
			if (range(0, count($args) - 1) === array_keys($args)) {
				// In that case, we have unnamed placeholders.
				$count = 0;
				$new_args = array();
				foreach ($args as $value) {
					if (is_float($value) || is_int($value)) {
						if (is_float($value)) {
							// Force the conversion to float so as not to loose precision
							// in the automatic cast.
							$value = sprintf('%F', $value);
						}
						$query = substr_replace($query, $value, strpos($query, '?'), 1);
					}
					else {
						$placeholder = ':db_statement_placeholder_' . $count++;
						$query = substr_replace($query, $placeholder, strpos($query, '?'), 1);
						$new_args[$placeholder] = $value;
					}
				}
				$args = $new_args;
			}
			else {
				// Else, this is using named placeholders.
				foreach ($args as $placeholder => $value) {
					if (is_float($value) || is_int($value)) {
						if (is_float($value)) {
							// Force the conversion to float so as not to loose precision
							// in the automatic cast.
							$value = sprintf('%F', $value);
						}

						// We will remove this placeholder from the query as PDO throws an
						// exception if the number of placeholders in the query and the
						// arguments does not match.
						unset($args[$placeholder]);
						// PDO allows placeholders to not be prefixed by a colon. See
						// http://marc.info/?l=php-internals&m=111234321827149&w=2 for
						// more.
						if ($placeholder[0] != ':') {
							$placeholder = ":$placeholder";
						}
						// When replacing the placeholders, make sure we search for the
						// exact placeholder. For example, if searching for
						// ':db_placeholder_1', do not replace ':db_placeholder_11'.
						$query = preg_replace('/' . preg_quote($placeholder) . '\b/', $value, $query);
					}
				}
			}
		}

		return $this->dbh->PDOPrepare($query);
	}

	public function execute($args = array(), $options = array()) {
		try {
			$return = parent::execute($args, $options);
		}
		catch (PDOException $e) {
			if (!empty($e->errorInfo[1]) && $e->errorInfo[1] === 17) {
				// The schema has changed. SQLite specifies that we must resend the query.
				$return = parent::execute($args, $options);
			}
			else {
				// Rethrow the exception.
				throw $e;
			}
		}

		// In some weird cases, SQLite will prefix some column names by the name
		// of the table. We post-process the data, by renaming the column names
		// using the same convention as MySQL and PostgreSQL.
		$rename_columns = array();
		foreach ($this->columnNames as $k => $column) {
			// In some SQLite versions, SELECT DISTINCT(field) will return "(field)"
			// instead of "field".
			if (preg_match("/^\((.*)\)$/", $column, $matches)) {
				$rename_columns[$column] = $matches[1];
				$this->columnNames[$k] = $matches[1];
				$column = $matches[1];
			}

			// Remove "table." prefixes.
			if (preg_match("/^.*\.(.*)$/", $column, $matches)) {
				$rename_columns[$column] = $matches[1];
				$this->columnNames[$k] = $matches[1];
			}
		}
		if ($rename_columns) {
			// DatabaseStatementPrefetch already extracted the first row,
			// put it back into the result set.
			if (isset($this->currentRow)) {
				$this->data[0] = &$this->currentRow;
			}

			// Then rename all the columns across the result set.
			foreach ($this->data as $k => $row) {
				foreach ($rename_columns as $old_column => $new_column) {
					$this->data[$k][$new_column] = $this->data[$k][$old_column];
					unset($this->data[$k][$old_column]);
				}
			}

			// Finally, extract the first row again.
			$this->currentRow = $this->data[0];
			unset($this->data[0]);
		}

		return $return;
	}
}

/**
 * @} End of "ingroup database".
 */
